A passenger conveyor (such as an escalator or a moving walk) is increasingly widely used in public places such as subways, shopping malls, and airports, and operation safety thereof is increasingly important.
The passenger conveyor has moving steps and fixed comb plates. The comb plates are fixed at an entry and an exit of the passenger conveyor. During operation, engaging teeth of the steps and Comb teeth of the comb plates are well engaged to each other, such that the steps can smoothly enter a return track and an external foreign matter is prevented from being taken into the passenger conveyor. Therefore, an engaging state between the engaging teeth of the steps and the comb teeth of the comb plates is very important for safe operation of the passenger conveyor. For example, when the engaging teeth of the steps are broken or the comb teeth of the comb plates are broken, cases such as an object carried by a passenger being entrapped into the passenger conveyor may easily occur, and the risk when a passenger takes the passenger conveyor greatly increases. For another example, when an external foreign matter such as a coin is entrapped, it easily causes misplacement of engagement, which will easily damage the steps and the comb plates, and bring in danger to the passenger.
Therefore, it becomes very important to discover an abnormal engaging state between the engaging teeth of the steps and the comb teeth of the comb plates in time.